Help! Water Leak in Rear Corner of Ceiling

[KATfishing]

Hi All - My 08 Yukon Denali was parked on the street (very slight incline) during the rain and when I opening the lift gate I noticed some water on the cargo mat on passenger side rear. It's wet and dripping in the corner of the ceiling. See pics, first of the wet ceiling corner and second of a loose weather strip on the top inside of the lift gate. However, thinking culprit might be a loose roof rack bolt... doesn't feel loose when I grip the rack. Anyone run into this? If it's the rack, how do I get those rear caps off to try tightening the bolt? (see pic 3) All ideas and advice appreciated.

 

[MD Tahoe 13]

Bumping up this thread. I am having the same issue in the same spot on my 2013 Tahoe. Did you replace the weather strip?